title: Accelerated myelination along fiber tracts in patients with hemimegalencephaly.
abstract: OBJECTIVE
  In infants with hemimegalencephaly, asymmetrical white-matter intensities suggestive of advanced myelination are observed as well as aberrant midsagittal fibers (AMFs) specific to hemimegalencephaly. Also noted are otherwise unreported abnormally enlarged periventricular fibers (APVFs) running anteroposteriorly along the caudate nucleus. This study investigated the degree of myelination and presence of aberrant fibers in hemimegalencephaly through a retrospective review of MRI scans in relation to histopathological findings.
  
  
  METHODS
  MRI scans of 24 infants with hemimegalencephaly (13 boys and 11 girls, 1-9 months old) were evaluated, focusing on the presence and signal intensities of AMFs and APVFs. White-matter signal intensities on T1- and T2-weighted imaging of the cerebral hemisphere were also evaluated and compared with the timetable for normal myelination. Surgical specimens were pathologically examined with Klüver-Barrera staining in four patients.
  
  
  RESULTS
  AMFs and APVFs were observed in 18 and nine patients, respectively, while 22 patients had accelerated myelination of the megalencephalic hemisphere that tended to extend along fiber pathways including AMFs and APVFs. In six cases, accelerated myelination even extended into the contralateral hemisphere via the corpus callosum or AMFs. Histopathological analysis identified hypermyelination with disarrayed myelinated fibers corresponding to MRI findings.
  
  
  CONCLUSIONS
  Accelerated myelination is frequently observed in patients with hemimegalencephaly and tends to extend along fiber pathways, including aberrant or abnormal fibers, as seen in 75% of hemimegalencephaly patients. Accelerated myelination may reflect propagation pathways of abnormal brain activity in such patients.
authors.affiliation: Department of Radiology, National Center Hospital of Neurology and Psychiatry, 4-1-1, Ogawahigashi-chyo, Kodaira, Tokyo 187-8551, Japan.
authors.forename: Kouhei
authors.initials: K
authors.lastname: Kamiya
authors.affiliation: Department of Radiology, National Center Hospital of Neurology and Psychiatry, 4-1-1, Ogawahigashi-chyo, Kodaira, Tokyo 187-8551, Japan. Electronic address: snoriko@ncnp.go.jp.
authors.forename: Noriko
authors.initials: N
authors.lastname: Sato
authors.affiliation: Department of Pathology and Laboratory Medicine, National Center Hospital of Neurology and Psychiatry, 4-1-1, Ogawahigashi-chyo, Kodaira, Tokyo 187-8551, Japan.
authors.forename: Yuko
authors.initials: Y
authors.lastname: Saito
authors.affiliation: Department of Radiology, National Center Hospital of Neurology and Psychiatry, 4-1-1, Ogawahigashi-chyo, Kodaira, Tokyo 187-8551, Japan.
authors.forename: Yasuhiro
authors.initials: Y
authors.lastname: Nakata
authors.affiliation: Department of Radiology, National Center Hospital of Neurology and Psychiatry, 4-1-1, Ogawahigashi-chyo, Kodaira, Tokyo 187-8551, Japan.
authors.forename: Kimiteru
authors.initials: K
authors.lastname: Ito
authors.affiliation: Department of Radiology, National Center Hospital of Neurology and Psychiatry, 4-1-1, Ogawahigashi-chyo, Kodaira, Tokyo 187-8551, Japan.
authors.forename: Yoko
authors.initials: Y
authors.lastname: Shigemoto
authors.affiliation: Department of Mental Disorder Research, National Institute of Neuroscience, National Center of Neurology and Psychiatry, 4-1-1, Ogawahigashi-chyo, Kodaira, Tokyo 187-8502, Japan.
authors.forename: Miho
authors.initials: M
authors.lastname: Ota
authors.affiliation: Department of Child Neurology, National Center Hospital of Neurology and Psychiatry, 4-1-1, Ogawahigashi-cho, Kodaira, Tokyo 187-8551, Japan.
authors.forename: Masayuki
authors.initials: M
authors.lastname: Sasaki
authors.affiliation: Department of Radiology, Graduate School of Medicine the University of Tokyo, 7-3-1, Hongo, Bunkyo-ku, Tokyo 113-8655, Japan.
authors.forename: Kuni
authors.initials: K
authors.lastname: Ohtomo
mesh_terms: D001921:Brain / Q000473:pathology*; D056324:Diffusion Tensor Imaging / Q000379:methods*; D005260:Female; D065705:Hemimegalencephaly / Q000473:pathology*; D006801:Humans; D007223:Infant; D007231:Infant, Newborn; D008297:Male; D009186:Myelin Sheath / Q000473:pathology*; D009413:Nerve Fibers, Myelinated / Q000473:pathology*; D009434:Neural Pathways / Q000473:pathology*; D015203:Reproducibility of Results; D012680:Sensitivity and Specificity
keywords: Diffusion tensor imaging; Epilepsy; Hemimegalencephaly; Myelination